Non-union Treatment in the arm, wrist, and fingers: A Multicenter Retrospective Study Contrasting Conventional Treatment with the Allogeneic Cortical Bone Screw (Shark Screw®)

doi:10.21203/rs.3.rs-4562491/v1

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Non-union Treatment in the arm, wrist, and fingers: A Multicenter Retrospective Study Contrasting Conventional Treatment with the Allogeneic Cortical Bone Screw (Shark Screw®)

https://doi.org/10.21203/rs.3.rs-4562491/v1

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Introduction: The cause of pseudarthrosis is the interaction of various biological and biomechanical factors with systemic and local interactions. Successful therapy consists of a combination of optimizing mechanical stability and activating biological factors. The conventional method for treating non-union is debridement and stabilization with metal hardware. But it leads to complications and a potential second operation for hardware removal. The human allogeneic cortical bone screw (Shark Screw®) provides a close contact between allograft and host bone, which is required for revascularisation and bone healing. The Shark Screw® merges human cortical bone properties with screw stability, addressing non-union surgery principles by integrating mechanical and biological aspects. Material and Methods: The retrospective-multi-center study included 31 patients, 11treated with the conventional method(metal hardware ± graft) and 20 patients with the Shark Screw® (±graft). Patient demographics, non-union location, autograft and/or allograft use, follow-up time, complications, union-rate, time-to-union and time-to-return to work were recorded. Results: Follow-up was 17 months in the conventional group and 12 months in the Shark Screw® group. The union rate was 72.7% in the conventional group and 95.0% in the Shark Screw® group. Time to union was significantly shorter in the Shark Screw® group with 12 weeks in comparison to 39 weeks in the conventional group. Conclusion The Shark Screw® presents a reliable option for treating non-unions in the shoulder, forearm, hand, and fingers. It demonstrates a low complication rate. The human allogeneic cortical bone screw (Shark Screw®) combines both stability and biology with a single transplant. The socioeconomic effect is another advantage using the Shark Screw®. Level of evidence: III

non-union

shoulder

arm

wrist and finger

human allogeneic cortical bone screw (Shark Screw®)

time to union

metal hardware removal

socio-economic effect

Physiological fracture healing is a biological outstanding achievement. It can be disturbed by many factors [1]. The cause of non-union seems to be an interaction of various biological and biomechanical factors with systemic and local interactions [1; 2]. Regarding local causes, unsuitable or faulty stabilization, possibly with long periods of reduced loading, pronounced soft tissue damage, reduced blood supply in the affected region and traumatic or iatrogenic destruction of the periosteum, former radiation and infection are considered to be permissive for failure of the fracture to heal [1; 2]. Gagnon et al. [3] summarize in their recent review that: ”Every non-union case is different in terms of bone defect, biology, mechanical stability, surgical technique and host factors…We might never see a level 1, high powered and robust study defining the efficacy, safety profile and cost-effectiveness”[3] because of the different procedures necessary to overcome non-union. Non-union results in prolonged pain and reduced functionality [4]. Socioeconomic costs are caused by the complex operation treatment strategies [4–7]. Therefore, successful therapy often consists of a combination of optimizing mechanical stability and activating biological factors [1; 7; 8]. For the biological activation of fracture healing the application of autologous cancellous bone is often used [2; 9–11], but its limited availability and the high donor site morbidity [9; 11] is a great disadvantage. The site of non-union can be augmented with bone graft. Allografts are an alternative and perform as autografts [9; 12]. The conventional method for treating non-union is the debridement of the non-union and the stabilization with metal plates and screws. But metal hardware leads to complications and a potential second operation for hardware removal. Complication rates between 30–60% are reported after total wrist arthrodesis and a re-operation rate between 19–64% [13]. Nwosu et al. describe in their recent review 3–31%[14] hardware related complications. Hardware removal was recorded between 6.8% after volar locking plate fixation of distal radius fractures in adults [14] up to 77% after arthrodesis for primary osteoarthritis of the trapezio-metacarpal joint [15–18]. Avoiding hardware removal and donor site morbidity while obtaining comparable results as with conventional methods would decrease economic burden and the higher risk for the patient.

The non-union rate in the shoulder is reported with 5% [19]. Non-union in long bones is recorded up to 30% [1]. Vanderkarr et al. [20] describe a 7.2% non-union rate for the humerus. In the forearm non-unions are reported to be between 0–60% [10; 21–23]. Non-union rates are described with 4% for the radius, with 7% for the ulna [2] and with 11% for the hand [8]. For the scaphoid, non-unions are reported between 0% and 18% and in some cases up to 63% [11; 24–27]. Treating scaphoid non-union arthroscopically with autograft from the distal radius and 4 pins resulted in 93.5% union [28]. Dislocated fractures, in particular seem to be prone to non-union [6; 29; 30]. Displaced scaphoid fractures are at risk for nonunion due to a variety of factors, including interfragmentary instability, retrograde vascular supply, and lack of soft tissue attachments on a largely cartilaginous surface [30; 31]. Non-union after arthrodesis of the proximal interphalangeal joint of the finger is reported with 3.9% using the compression screw and 8.6% after interosseous wiring [32]. Fractures with severe soft tissue trauma are also at increased risk of non-union [20].

To avoid progression to arthrosis of the scaphoid there are 3 major aims: restauration of the form of the scaphoid, restauration of the carpal alignment and bony consolidation of the scaphoid [25]. Despite improvement in surgical procedures treating non-union, there is no consensus over the optimal treatment option.

For certain age groups Mills at al. [33] described a non-union rate up to 9% and 80 non-unions per 1000 fractures in the shoulder per year for the age group between 35–45 years [33]. This is mainly true for male patients, for female patients an increase in the incidence is reported with age [8; 34].

Using the human allogeneic cortical bone screw (Shark Screw®) is a new option to treat non-unions[7]. The cortical bone screw provides a close contact between allograft and host bone, which is required for revascularisation and healing as described by Basile et al. [35] and confirmed by Brcic for the allogeneic cortical bone screw [36]. It is described that (metal) screw fixation disrupts the internal vascularity [37; 38] more than a K-wire and hence reduces the potential benefits of vascular grafts [37]. Perren et al. [38] describes that a plate used for e.g. radius fixation inhibits the blood reaching or leaving the bone. This complication is avoided by using the cortical bone screw because vascularization is not disrupted. The success of the graft may also depend on the quality of the bone bed from which most of the revascularization arises [36; 39]. The processing, preservation and sterilization (via irradiation or chemically sterilized) of allograft bone may influence its biophysical and general biological properties [39]. The goal of using bone allograft is to initiate a healing response from the host bed that will produce new bone at the host-graft interface and within the porous body of the graft material [39]. The mechanical stability of the graft is of vital importance [39] and is given by the design of the Shark Screw® as a set screw. For the human allogeneic cortical bone screw this process was shown after 10 weeks [36]. Recent publications show that, when using the Shark Screw, the union rate is between 94–100% for fracture treatment, arthrodesis and non-union [40–43] and thus similar to union rates with conventional methods.

The multicentred retrospective data analysis presented here aims to compare the outcome of non-union treatment with 1) conventional methods (metal crews/plates/nails ± graft and 2) the human allogeneic cortical bone screw (Shark Screw®) in upper extremities. We recorded patient demographics, follow up time, union rate, time to union, time to return to work, complications, and percentage of hardware removal. We collected data from clavicula, humerus, radius, ulna, the scaphoid, and the finger joints.

Approval from the local Institutional Review Boards (IRBs) was received before the study's commencement, and the reference numbers are as follows: 1146/2023 (Ethik-Kommission of the Johannes Keppler University Linz), and M2023-25 (Ethik-Kommission Kärnten). The study was conducted in accordance with the Declaration of Helsinki. Informed consent to participate was waved by the institutional review boards.

Study design and patient population

This study was designed as a retrospective multicentred study. Clinical and radiographic data were collected from the medical charts of 31 patients who underwent non-union surgery on the shoulder, arm, and fingers between 2016 and 2022.

The specific treatment method for non-union was not a selection criterion. Our study included a total of 31 patients, with 11 patients (37%) in the conventional treatment group and 20 patients (64%) in the Shark Screw® group. Patient demographics are presented in Table 1.

Table 1

Patient Data
	Conventional treatment (metal hardware ± graft)		Shark Screw® treatment (Shark Screw® ± metal plate)
	Number of patients	Mean ± SD	Number of patients	Mean± SD
Number of patients	11	-	20	-
Age [years]	11	40.8 ± 19.9	20	54.8 ± 15.7*
BMI [kg/m²]	11	25.1 ± 6.4	20	25.1 ± 4.7
Gender [male/female]	6/5	-	10/10	-
Smoker [yes/no]	5/6	-	5/15	-
Comorbidities [yes/no]	4/7	-	9/11	-
Non-union revision following: Surgical fracture treatment Elective surgery (arthrodesis, osteotomy) Conservative fracture treatment	3 1 7	- - -	8 7 5	- - -
Aseptic/septic	10/1	-	20/0	-
*p = 0.03909 vs. conventional group

Patients from two treatment groups were evaluated: the conventional treatment involving metal hardware (screws/plates) ) with or without bone graft (Table 2), and the Shark Screw® procedure.

Table 2

Localization of Pseudarthrosis
Anatomic localization of non-union		Conventional treatment (metal hardware ± graft)	Shark Screw® treatment (Shark Screw® ± metal plate)
	Number of patients	11	20
Shoulder	Clavicular	3	1
	Shoulder (Latarjet)	0	1
Arm	Humerus	1	3
	Ulna	1	1
	Radius	1	1
Hand	Scapho-Trapezo-Trapezoidal (STT)	0	1
	Wrist	0	1
	Repetitive Strain Injury (RSI)	1	0
	Scaphoid	3	4
Finger	PIP3	1	0
	DIP1 CP	0	3
	DIP2,3,4	0	1
	DIP2,3,5	0	1
	MCP 2	0	2

The comorbidities included Diabetes Mellitus Type II, COPD, mutilating chronic polyarthritis, arterial hypertension, adeno carcinoma, (allergic) asthma bronchial, Lupus erythematosus, osteoporosis, foramen ovale, deep vein thrombosis, varicose, benign prostatic hyperplasia.

Inclusion Criteria

To be eligible for inclusion in the study, patients were required to have at least one follow-up visit at least 6 months post-surgery or until bone healing was documented. These cases encompassed non-union after elective procedures (arthrodesis and osteotomy), after surgical fracture treatment, and after conservative fracture treatment (Table 1).

Exclusion Criteria

We excluded non-unions related to tumour-related cases.

Surgical procedures

Surgical procedures vary with location of the non-union. For using the cortical bone screw surgical procedures were described before for different locations [40] of the hand, for scaphoid fractures [42], and for distal interphalangeal joint arthrodesis [43].

We recorded the following parameter: Non-union location for revision (Table 2), autograft and allograft use, follow up time, complications, union rate, time to union and time to return to work (Table 3).

Table 3

Clinical Data and Outcome
		Conventional treatment (metal hardware ± graft)				Shark Screw® treatment (Shark Screw® ± metal plate)
		Number of patients		Mean ± SD/%		Number of patients		Mean ± SD/%
Number of patients	11		-		20		-
metal hardware use additional to Shark Screw® metal left in from previous surgery	11 (per definition) - -		- - -		- 2 (1xprothesis) 2		- - -
Autograft use Iliac crest Medial femoral condylar span (MFC) Lateral femoral condylar span (LFC) Allograft use DBM putty cortical span	2 2 2 0 0		- - - - -		- - - 7 1		- - - - -
Follow up [weeks]	11		71.0 ± 41.0		20		50.5 ± 36.4^&
Complications [yes/no][%]	4/7		36.4		1/19*		5.0
Metal hardware removal [%]	7		63.6		1^%***		5.0
Bony union rate [%] Partial union [%] Non-union [%]	8 1 2		72.7 9.1 18.2		19 1 0		95.0 5.0 0.0
Time to Union [weeks]	8		38.8 ± 26.3		19		12.4 ± 5.4****
Return to work [weeks]	10		25.3 ± 16.3		20		12.0 ± 5.5**
^&p = 0.16055; p = 0.02311; p = 0.00238; ^%Hardware removal from previous surgery; p = 0.000357; **p = 0.000247

Complications

We defined non-union and partial union after 6 months, osteonecrosis, screw loosening or screw breakage as a complication.

Statistics

Data are presented as mean ± SD. Due to the non-Gaussian distribution of the data, non-parametric Kruskal–Wallis ANOVA was used for calculating significant differences in quantitative values. Ordinal values were evaluated with contingency tables using Fisher’s exact test for significance. A p-value < 0.05 is considered to be significant with a power > 0.8. All statistical analyses were performed using Origin Pro statistical software (OriginPro, version 2023; OriginLab Corporation, Northampton, MA).

Patient average age was 41 years in the conventional group and 55 years in the Shark Screw® group, this difference was statistically significant (p = 0.03909). Patients average BMI was 25 kg/m². In the conventional group and in the Shark Screw® group were smoker, 45% and 25%, respectively. 52% were male patients (Table 1).

Except for age, patient demographics were not significant different between the conventional group and the Shark Screw® group (Table 1). Patients in the Shark Screw group were significantly older.

For the conventional group in 4 cases metal screws were used, in 3 cases plates, in 2 cases K-wires, 1 mini-fixateur and in 1 case a prothesis was placed. In the Shark Screw® group in 1 case the metal hardware was left in. Autograft was used only in the conventional group in 6 cases (Table 3). Allograft was not used in the conventional group but in 8 cases (DBM putty (7 cases) and one cortical span) in the Shark Screw® group.

Follow up was 17 months in the conventional group and 12 months in the Shark Screw® group.

The union rate was 72.7% (8 of the 11 patients) in the conventional group and 95.0% (19 of the 20 patients) in the Shark Screw® group. Time to union was significantly shorter in the Shark Screw® group with 12 weeks in comparison to 39 weeks in the conventional group (p = 0.000247). Smoking delayed union in the conventional group, but it did not reach statistical significance, but not in the Shark Screw® group (data not shown). There was an earlier return to work for the Shark Screw® group, with 12 weeks for the Shark Screw® group and 25 weeks for the conventional group (p = 0.00238).

Complications were low in both groups with 4 in the conventional group (2 non-unions, one of them with osteonecrosis, 1 partial union and 1 screw loosening) and 1 in the Shark Screw® group (partial union). Non-unions were recorded in patients with an age of 35 and 59 years, whereas patients obtaining only partial unions were older (55 years and 78 years). All patients with non-unions or only partial unions were non-smokers. Except for the 59-year-old patient (Lupus erythematosus) in the conventional group, none of the patients with complications had co-morbidities at the time of surgery. Metal removal in the conventional group was performed in 7 of the 11 patients (64%) compared to 1 patient (5%) in the Shark Screw® group. The one patient in the Shark Screw® group had metal hardware from a previous surgery, which was left in place during revision surgery, but removed later.

A failed thumb IP-arthrodesis of a 72-year-old patient with chronic polyarthritis is depicted in Fig. 1a-c and was treated with 1 Shark Screw®, union was recorded after 12 weeks and the Shark Screw® totally remodeled into host bone after 21 months (Fig. 1c). The revision after a failed arthrodesis of a middle finger with a metal screw of a 63 years-old patient is shown in Fig. 1d-i for the left hand and in Fig. 1j-o for the right hand. The X-ray after the first treatment is presented in Fig. 1d-e. Even hardware removal did not lead to union 31 months after surgery. For revision one Shark Screw was placed (Fig. 1f-g) and union was obtained after 26 weeks. 36 months after revision surgery the Shark Screw® is nearly totally remodelled (Fig. 1h-i). The treatment of a non-union of a middle finger of the right hand is presented in Fig. 1l-q: The Herberden Osteoarthrosis was bridged with a 3 mm metal screw in the first attempt (Fig. 1j-k), even after 21 months no union was recorded (Fig. 1l-m). Revision was performed with one 3.5 mm Shark Screw®. Starting the consolidation is visible 6 weeks after revision (Fig. 1n-o).

totally remodelled. j-o: The middle finger of the right hand. j-k: The Herberden osteoarthrosis was bridged with a 3 mm metal screw in the first attempt, l-m; even after 21 months no union was recorded. Revision was performed with one 3.5 mm Shark Screw®. n-o: Starting the consolidation is visible 6 weeks after revision

A 31-year-old patient with a non-union of the scaphoid is presented in Fig. 2a-g. Revision was performed with 1 Shark Screw® (Fig. 2b). Union was obtained after 8 weeks (Fig. 2c). After 35 months the Shark Screw® is totally remodeled into host bone (Fig. 2d). An 82-years-old patient was treated with 2 Shark Screws® (Fig. 2f) to overcome the non-union (Fig. 2e) of the scaphoid-trapezoid-trapezium-arthrodesis. Union was detected 8 weeks after revision surgery. 14 months after revision the Shark Screw® is not any more visible (Fig. 2g). In Fig. 2h-l we present the non-union obtained for the scaphoid after conventional treatment even though autograft was used. Figure 2h pre-revision X-ray. Figure 2i intraoperative fluoroscopy using a vascularized femur condylar span which was attached to the aorta radialis. The span was stabilized with 4 K-wires. 12 weeks after surgery is presented in Fig. 2j with the non-union still visible. Shock-wave therapy did not improve the situation after 8 month (Fig. 2k). Five years after revision, the necrosis of the proximal pole is visible, but the patient is nearly pain-free (Fig. 2l).

A 59-year-old patient was treated for non-union after using a humerus nail after a fall at home (Fig. 3), 10 months after initial surgery non-union was recorded (Fig. 3a). For revision, non-union debridement was performed, the nail was removed and replaced with a 9-hole plate. Non-union was additionally bridged with 2 Shark Screws®. Four weeks after revision the Shark Screws® are still well visible and union not yet observed (Fig. 3b). Eight weeks after revision (Fig. 3c) remodelling is visible in part of the former non-union area. Union was recorded 12 weeks after revision surgery. Figure 3d shows union and full remodelling of the Shark Screws® 1-year post-revision. A radius-non-union in a 39-year-old patient is shown in Fig. 3e-k. As the former radius plate was bent, the radius was shortened in relation to the ulna (Fig. 3e-f). During the revision operation, the plate on the radius was replaced and the radius was restored to its original length. The resulting bone defect was filled with an allogeneic cortical block and DBM putty. In addition, the bone defect was stabilized and bridged with 2 Shark Screws®(Fig. 3g-h). Union was obtained after 12 weeks; Metal hardware was removed 1 year after revision surgery (Fig. 3i-k).

The nonunion of the epicondyle of the lateral humerus of an 80-year-old patient is presented in Fig. 4. Pre-revision X-ray and CT scan are shown in Fig. 4a-b. Non-union was treated with 3 Shark Screws® (Fig. 4c) and union was observed after 10 weeks. Figure 4d represents the X-ray after 4 months and 21 months after revision the Shark Screws® are totally remodelled into host bone (Fig. 4e).

A humerus shaft non-union of a 40-year-old patient is depicted in Fig. 5a-f. The nail was left in, but the non-union was bridged with 3 Shark Screws® (Fig. 5c-d). Union was recorded after 7 weeks. 8 months after revision the Shark Screws® were remodeled to host bone and are not any more visible (Fig. 5e and ). A failed Laterjet in a 35-year-old patient was treated with 1 Shark Screw® (Fig. 5g-i). The metal screws were taken off (Fig. 5g). No debridement of the non-union was performed, only the bone bed was prepared for the Shark Screw® (drilling and thread cutting). 1 Shark Screw® was used for revision (Fig. 5h). Union was observed 2 months after surgery. 4 months after surgery the Shark Screw® is totally remodelled into host bone (Fig. 5i).

In Fig. 6a-d we show the revision of the non-union of a clavicula of a 64-year-old patient. Former metal hardware (Fig. 6a-b) was removed in the same session and 2 Shark Screws® were used for revision. Union was obtained 12 weeks after revision (Fig. 6c). 15 months after revision bone union is visible and the Shark Screws® are totally remodelled into host bone. In Fig. 6e-g we present the case of non-union union after osteomyelitis of a 52-year-old patient after a fall at home. The fracture was anatomically reduced after pseudoarthrosis removal, insertion of microvascular pedicled MFC spans and bridging osteosynthesis with a 10-hole lateral clavicle plate (Arthrex, Naples, FL, USA, Fig. 6f). With complete union 1 year after revision (Fig. 6g).

A case of a non-union of a scaphoid fracture with conservative treatment (Fig. 7a) is shown in Fig. 7a-e. Revision was performed using Linscheid maneuver, correction of Humpback deformity, using an autologous iliac crest cortical bone span and a Herbert Screw (Fig. 7b). Figure 7c shows the X-ray after 2 months. Union was observed 6 months after surgery (Fig. 7d). Metal hardware was removed 1 year later. Figure 7e shows an X-ray 18 months post revision. Pseudoarthrosis after scaphoid fracture in the middle third after surgical treatment with angle stable Medartis scaphoid plate (1.5 mm) is presented in Fig. 7f-h. Revision was performed including metal removal (Fig. 7f), elimination of the humpback deformity and pseudoarthrosis bridging with one 3.5 mm Shark Screw®. Figure 7g represents the case 6 weeks after revision surgery. Two years after revision we recorded increasing callus formation, the pseudoarthrosis is still visible centrally, the Shark Screw® is now completely resorbed, the fracture is not yet completely united (Fig. 7h).

The most important finding of this study is, that surgical treatment of non-union with the human allogeneic cortical bone screw (Shark Screw®) outperformed conventional treatment (metal hardware) with a 95% bone healing rate with a shorter time to union (26 weeks earlier) and a faster return to work (13 weeks earlier). The Shark Screw® group had fewer complications, with only one cases of partial union recorded, which occurred after scaphoid revision surgery. An advantage of the Shark Screw® is its avoidance of metal components, which may further cause problems. In 2 cases the metal hardware from previous surgeries was left in, in 1 case the old metal hardware was replaced with new metal hardware and in 1 case an ulna head prothesis was used additionally to the Shark Screws® used. It is possible to combine the human allogeneic cortical bone screw with metal hardware. The use of the Shark Screw® avoids donor site morbidity and improves bone healing.

The non-union-rate depends on the location of the fracture and is reported to be the highest in the shoulder, followed by the upper arm and the forearm and is lowest in the hand [33]. In contrast Reeh et al. describes that the hand has the highest probability for non-union [8]. Non-union is described in the humerus with 7.2% [20] − 9%[34; 44] and for non-union treatment in the humerus with 16% [3], in the ulna with 7% [44] and 5%[44] in the radius. We recorded non-union in the ulna and in the scaphoid and partial union again in the ulna and in the scaphoid, which confirms the literature. Union rates for revision of scaphoid non-union were reported with 50%-100% [11; 25; 28; 30; 42; 45–47]. Millrose et al. [32] describes a non-union rate between 3.6% and 8.6% for PIP joint arthrodesis depending on the technique used. The union rate in our cohort was 73% and 95% in the conventional group and in the Shark Screw® group, respectively. In the conventional group we had 1 non-union and 1 partial union in the ulna. Additional, in the conventional group there was 1 non-union in the pole fraction of the scaphoid, which is known to show higher non-union rates than for waist or distal fractures of the scaphoid [42; 47]. In the Shark Screw® group we did not have any non-union. The partial union in the Shark Screw® group was recorded in one case of scaphoid (waist fraction) non-union-revision.

Time to union for the clavicula after non-union was reported with 3–8 weeks [48]. Literature reports treating forearm non-unions with allograft resulted in union after 102 days (14 weeks) and after 117 days (17 weeks) for the autograft group, when using plates and nails [12]. For the forearm 6 months were described for the time to union [10]. Time to union was 3.8 months without bone grafting [26]. After non-union revision time to union is described after 3–4 months [28; 42]. Others report 15 months until union was obtained for scaphoid fractures [47]. We could observe a significant shorter time to union in the Shark Screw® group (12.4 weeks), which was on the shorter end of the results described in the literature. Time to union in the conventional group was longer (39 weeks), with 2 patients (both smokers) having extremely long time to union (74 and 78 weeks). But still this value is in the range described in the literature [47].

The complication rate using the conventional methods is reported to be between 4 and 33% for major complications [11; 49] and up to 44% including minor complications [49]. Lari et al. [50] reported in his review article a complication rate of 14% after distal radius fractures involving the volar rim. In our study we recorded 4 complications (36%) in the conventional group, 2 non-unions, 1 partial union and 1 case of screw loosening. In the Shark Screw® group there was only 1 complication (5%) of a partial union which confirms reports in the literature [51].

The hardware removal rates were reported with 7.5% [52], 20% [11], 22% [50] and 65% [17]. Removal of internal fixation is described with an incidence of 1.92/100000 person years and 20,385 cases between 2007–2019 [8]. In our patient cohort the hardware removal rate was 63.6% in the conventional group and 5% (1 patient) in the Shark Screw® group which was significant different (p = 0.000794). The one patient in the Shark Screw® group had hardware from previous surgeries, which were left in place during revision.

Rolo et al. [12] reported a return to work after 9.4 months in the allograft group and 12.6 months in the autograft group when using metal plates for treating forearm non-unions [12]. These results described are longer than observed in our study. After 4-corner fusion using bioabsorbable plates, return to work was described with 4.5 months [53] which is longer than our values in the Shark Screw® group but shorter than in our conventional group. After fixation of scaphoid fractures with staples, return to work was described with 10 weeks [52], which is similar to our observation in the Shark Screw® group, but primary fractures and non-unions were not separately analyzed. In our cohort, the return to work was 13 weeks earlier in the Shark Screw® group (12 weeks) than in the conventional group (25 weeks), which was statistically significant (p = 0.00238). Further studies should be performed to support this findings.

Non-union is described more in male patients aged between 30 and 50 years [8; 44], which may be attributed to more high energy trauma [5]. This was not true in our cohort. There were 2 male and 2 female in the group of partial union and non-union. Reeh et al. [8] describes that male patients under 30 years are at the highest risk for non-union, whereas for female the risk of nonunion increases with age. The latter statement was true for our patient cohort, because the 2 oldest patients with non-union/partial union were female, the male patients with non-union/partial union were younger (35 and 55 years). We can confirm the middle age group for higher rates of non-unions in male (35 years) and the higher age in female (59 years), whereas the patients with partial unions were older (55 and 78 years). Ekegren et al. [34] describes that patients between the age of 55–64 years are more than twice as likely to be resubmitted to the hospital for non-union than younger, which confirms our findings.

An interesting observation in our study is that 32% of the patients which were treated for non-union, were smoker, whereas in the general European public around 20% are smoker, with 28% in Turkey and, 11% in the United States. Especially in the conventional group the percentage of smoker was high (45%). We could not detect that time to union was significantly delayed for smokers [54].

The incidence of non-union in the upper arm and forearm is described with 1.3/100,000 [8; 55], and for the hand with 2.9–3.08/100,000 [8; 55]. This sums up to 5,824 − 13,798 patients per year in Europe. Walter et al. [55] describes a re-imbursement for nonunion revision between €2900 (hand) and €5095 (forearm). We obtained a reduction of the non-union rate by 22% (p = 0.12096). Because this difference was not significant, we would use a reduction of 10% for our calculations. When using the human allogeneic cortical bone screw the number of non-unions could be reduced by at least 10% (700 patients). Calculating with €4000 per reimbursement this accumulates to €2,800,000 per year for the health system in Europe. Additionally, there would be savings because there is no need for hardware removal (as described by Reeh et al. [8]) and the savings for the patient for lost wages.

In conclusion, the Shark Screw® presents a reliable option for treating non-unions in the shoulder, forearm, hand, and fingers. It demonstrates a low complication rate. The human allogeneic cortical bone screw (Shark Screw®) combines both stability and biology with a single transplant. This dual functionality is unmatched by any other material, particularly one that integrates seamlessly with the host bone in accordance with its biology. As Elliott et al. [56] describes: the tissue that forms in and around a fracture should be considered a specific functional entity [56]. This ‘bone-healing unit’ produces a physiological response to its biological and mechanical environment, which leads to the normal healing of bone[56] which was confirmed for the human allogeneic cortical bone screw [36]. The Shark Screw® forms a bone healing unit with the surrounding tissue which is in constant exchange with the host tissue. The presented data show that the use of the human allogeneic cortical bone screw (Shark Screw®) alone or in combination with (remaining) metal hardware results in shorter time to union and earlier return to work after non-union revision surgery compared to the conventional treatment. The potential for cost savings (reduction in non-union rate and reduction in hardware removal after healing) favors utilization of the Shark Screw® for the revision of a non-union. Further studies have to be performed to underline these findings.

Limitation of the study

The retrospective design of the study is a limitation. The involvement of multiple surgeons led to variations in surgical protocols, therefore they are not described in detail in this study. Due to the positive impression after the first treatments with the human allogeneic cortical bone screw the treatment with the conventional methods was more and more diminished and thus the groups do not have similar patient numbers. Additionally the patients in the conventional group are significantly younger, which should be kept in mind when interpreting the data.

Competing Interests

Klaus Pastl is one of the CEOs of Surgebright GmbH, Wolfgang Palle received a travel grant from Surgebright and support for attending a workshop, all other authors do not have any conflict of interest for the reported study.

Funding:

no funding

Author Contribution

E.H., K.P., G.H.B.: Conceptualization and methodology; K.P., E.H., W.P.G.J.: Surgery; G.H.B., K.P., E.H.: formal analysis and investigation; G.H.B., K.P., E.H.: Writing original draft preparation. All authors reviewed the manuscript.

Acknowledgement:

non

Ethical approval:

Consent to Participate:

Informed consent to participate was waved by the institutional review boards (Ethik-Kommission of the Johannes Keppler University Linz and Ethik-Kommission Kärnten due to the retrospective data analysis and was not obtained.

Conflict of Interest:

Generative AI

We did not use generative AI for any part of the manuscript.

Submission declaration

The manuscript has not been published previously and is not under consideration for publication elsewhere. Its publication is approved by all authors and tacitly or explicitly by the responsible authorities where the work was carried out, and that, if accepted, it will not be published elsewhere in the same form, in English or in any other language, including electronically without the written consent of the copyright holder.

Data Availability

Data is provided as supplemental information

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Competing interest reported. Klaus Pastl is one of the CEOs of Surgebright GmbH, Wolfgang Palle received a travel grant from Surgebright and support for attending a workshop, all other authors do not have any conflict of interest for the reported study.

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Non-union Treatment in the arm, wrist, and fingers: A Multicenter Retrospective Study Contrasting Conventional Treatment with the Allogeneic Cortical Bone Screw (Shark Screw®)

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Abstract

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Introduction

Material and Methods

Study design and patient population

Inclusion Criteria

Exclusion Criteria

Surgical procedures

Complications

Statistics

Results

Discussion

Conclusion

Limitation of the study

Declarations

Funding:

Author Contribution

Acknowledgement:

Data Availability

References

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