Use of an anterolateral distal tibia Locking Compression Plate for the management of acromion pseudoarthrosis in an osteogenesis imperfecta patient: a case report

Osteogenesis imperfecta (OI) is an inherited disorder that is relatively rare, affecting the genes encoding Type I collagen. Physical manifestations may include blue sclera, triangular facial shape, macrocephaly, hearing loss, defective dentition, barrel chest, vertebral compression and scoliosis, limb deformity, joint laxity, and fractures.1Jones D. Hosalkar H. Jones S. The orthopaedic management of osteogenesis imperfecta.Curr Orthop. 2002; 16: 374-388https://doi.org/10.1054/cuor.2002.0299Abstract Full Text PDF Scopus (4) Google Scholar Although certain fractures such as transverse humerus and olecranon fractures are known to be linked with OI,6Peddada K.V. Sullivan B.T. Margalit A. Sponseller P.D. Fracture patterns differ between osteogenesis imperfecta and routine pediatric fractures.J Pediatr Orthop. 2018; 38: e207-e212https://doi.org/10.1097/BPO.0000000000001137Crossref PubMed Scopus (18) Google Scholar the association of acromion fractures with OI is not found in the current literature. Fracture of the acromion is a rare occurrence in a native shoulder (<1% of all fractures5Nissen C.W. The acromion: fractures and Os acromiale.Oper Tech Sports Med. 2004; 12: 32-34https://doi.org/10.1053/j.otsm.2004.04.010Crossref Scopus (8) Google Scholar) and consequently, the rate of nonunion of acromial fractures is not clearly reported in the existing literature. In contrast, acromial fractures are reported as a known complication associated to reverse total shoulder arthroplasties (up to 3%-11%).2Joyce C.D. Seidl A.J. Managing acromial fractures: prevention and treatment, both nonoperative and operative.Ann Joint. 2019; 4: 1https://doi.org/10.21037/aoj.2018.12.03Crossref Scopus (8) Google Scholar In most cases, acromial fractures of the native shoulder are managed nonoperatively and heal well. However, it is hypothesized in the literature that symptoms from a base of the acromion fracture are unique because the mechanical pull from both deltoid and trapezius results in more symptoms, tendency for instability, and puts the patient at an increased risk of developing pseudoarthrosis.4Malavolta E.A. Assunção J.H. Sunada E.E. Gracitelli M.E. Neto A.A. A stress fracture of the base of the acromion: a case report.BMC Musculoskelet Disord. 2014; 15: 302https://doi.org/10.1186/1471-2474-15-302Crossref PubMed Scopus (9) Google Scholar,9Wahlquist T.C. Hunt A.F. Braman J.P. Acromial base fractures after reverse total shoulder arthroplasty: report of five cases.J Shoulder Elbow Surg. 2011; 20: 1178-1183https://doi.org/10.1016/j.jse.2011.01.029Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar Due to the rarity of the fracture itself and the even more rare need for surgical fixation, there is limited availability for proper hardware (precontoured and/or locking) for open reduction and internal fixation of this type of fracture. Described surgical techniques for these fractures include plates and screws, and tension band wiring with or without bone grafting.4Malavolta E.A. Assunção J.H. Sunada E.E. Gracitelli M.E. Neto A.A. A stress fracture of the base of the acromion: a case report.BMC Musculoskelet Disord. 2014; 15: 302https://doi.org/10.1186/1471-2474-15-302Crossref PubMed Scopus (9) Google Scholar,9Wahlquist T.C. Hunt A.F. Braman J.P. Acromial base fractures after reverse total shoulder arthroplasty: report of five cases.J Shoulder Elbow Surg. 2011; 20: 1178-1183https://doi.org/10.1016/j.jse.2011.01.029Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar Malavolta et al4Malavolta E.A. Assunção J.H. Sunada E.E. Gracitelli M.E. Neto A.A. A stress fracture of the base of the acromion: a case report.BMC Musculoskelet Disord. 2014; 15: 302https://doi.org/10.1186/1471-2474-15-302Crossref PubMed Scopus (9) Google Scholar used a standard 6-hole Locking Compression Plate (LCP) with locking screws to achieve the necessary fixation of a fractured acromion. More recently, Kurahashi et al3Kurahashi S. Takeda S. Mitsuya S. Makihara K. Yamauchi K.I. Plate fixation of acromion fracture using a mesh plate.Trauma Case Rep. 2021; 33100470https://doi.org/10.1016/j.tcr.2021.100470Crossref PubMed Scopus (3) Google Scholar reported the use of a “mesh plate” in 2 acute cases. This paper discusses a case report of a woman with OI who presented with a symptomatic displaced pseudoarthrosis of the base of her acromion. We describe the surgical considerations, challenges, and the technique we utilized to solve this unusual clinical problem. This patient agreed to have her history, physical examination findings, and imaging reported in the literature. A 36-year-old, right-handed dominant, female patient was referred to our service regarding an injury to her right shoulder. She specifically presented for a painful pseudoarthrosis of her acromion. She fell on her right shoulder one year prior to presenting to our service. All nonoperative methods of management had been exhausted, including rest, sling, low-intensity pulsed-ultrasound and physiotherapy. Her past medical history included OI type 3 with history of multiple fractures. Her past upper extremity injuries included 2 forearm fractures, 3 clavicle fractures, and 1 humerus fracture. She had a history of a seizure disorder that predisposed her to falls and secondary injuries. She denied any prior shoulder pain/injury in the past. She was not working at the time of presentation. She had quit smoking 18 months ago, and consumed one alcoholic beverage per month. She presented to us for final surgical fixation since she had a painful displaced nonunion on her dominant side that limited her daily activities and prevented her from looking for gainful employment. The physical examination showed a very thin woman with blue sclera and triangular facial shape. She had no shoulder deformity. She presented with a slightly decreased range of motion of 145° of forward elevation (vs. 160° forward elevation with left shoulder), and external rotation to 55° (compared to 70° on opposite side). The main limiting factor in her range of motion was pain. Her pain was focal and very well localized over the acromion, at the pseudoarthrosis site. Her bicipital grove was not tender. Greatest pain was elicited with specific examination of infraspinatus, but not with the remainder of the rotator cuff muscles testing. Her muscle strength was slightly reduced due to pain. Prior imaging was negative, with no prior fracture, no bone loss, and no basi-os acromial. X-rays at the time of the consultation with our service demonstrated (Fig. 1) an unusual position of the acromion (arrow, Fig. 1, B). The computed tomography scan (Fig. 2) provided greater details, demonstrating nonunion of a distracted acromion fracture that was about 9 mm displaced with an acromial maximum bone thickness of only 8 mm.Figure 2Preoperative 3D CT of the right shoulder demonstrating bone loss at nonunion site with arrows pointing at the acromion. (A) Posterior views. (B) Postero-superior view. CT, computed tomography.View Large Image Figure ViewerDownload Hi-res image Download (PPT) This patient’s peculiar presentation with displaced pseudoarthrosis of the acromion in the setting of OI posed a challenging surgical problem. Her small stature in conjunction with OI could potentially prevent getting good purchase in her bone if using traditional hardware. Her acromion was short from front to back and its thickness was at most 8 mm: this was a significant problem as the shortest available screw measured 10 mm. There was also some local bone loss from the chronicity of this nonunion. Lastly, the sudden transition from a stiff plate to poor quality bone could potentially cause a stress riser, increasing risk of a secondary fracture medial to the plate. After reviewing the literature on acromial nonunions and considering all types of plates available for this problem, we elected to use a locking implant that would allow us to have a large amount of small diameter locking screws in the acromion. This implant also had to have an angle close to 90° to accommodate for her acromion-spine bend. The best plate that would fit those requirements was an LCP 3.5-mm anterolateral distal tibial locking plate from DePuy-Synthes (Raynham, MA, USA). In addition, we planned to use an allograft to: (1) graft the pseudoarthrosis site (in addition to autogenous iliac crest bone chips), (2) account for the bone loss and augment the local bone stock at the nonunion site, (3) increase the thickness of her bone for better screw purchase, and (4) provide structural support. We also expected to use cancellous autograft bone chips from the ipsilateral antero-superior iliac crest for its osteoinductive and osteoconductive properties. The patient was placed in a “sloppy” lateral decubitus position, allowing access to the right antero-superior iliac crest as well as the postero-supero-lateral right shoulder. Incision was made along the posterior scapular spine. The deltoid and trapezius were then elevated off the postero-lateral scapular spine. The nonunion site was localized at the junction between the scapular spine and the acromion. The pseudoarthrosis was then taken down in its entirety until bleeding bone was encountered on both sides. We exposed the anterior scapular spine, in the posterior aspect of the supraspinatus fossa. During the dissection, we took great care to avoid the suprascapular nerve located at the base of the scapular spine. The acromion was then reduced with sharp reduction clamps. A malleable plate template was used to determine the contour of the under surface of the acromion along with the anterior aspect of the scapular spine. A proximal humerus allograft was utilized and an appropriately sized and tailored graft that fit the contoured malleable template was cut out, and then shaped to fit snugly under the acromion (Fig. 3, A). This was then affixed temporarily to the acromion with high strength sutures and clamped in place to accept our DePuy-Synthes LCP 3.5-mm anterolateral distal tibia locking plate. The plate was bent down to shape it to fit the scapular spine and acromion (Fig. 3, B). Compression of the allograft with the native bone was achieved through compression screws in the plate. The iliac crest was harvested to serve as biologically active cancellous autologous bone graft in and around the pseudoarthrosis reconstruction site and around the allograft and the scapular spine. After complete fixation, the range of motion was examined to ensure no part of the construct would impinge. Incision was closed with #1 Vicryl followed by 2-0 Vicryl (Ethicon, Johnson & Johnson, New Brunswick, NJ, USA) and finally 3-0 Monocryl (Ethicon, Johnson & Johnson, New Brunswick, NJ, USA) for skin along with Steri-Strips (3M, Saint Paul, MN, USA). The arm was then placed in Velpeau sling for 6 weeks. The patient was seen 2 weeks, 6 weeks, and 4 months after surgery for follow-up visits. She had significant improvement in her symptoms following the surgery. At 4 months, she was able to perform activities with her dominant arm just as she had done prior to the fracture and she was actively looking for work. Her range of motion was complete and pain free and her x-rays demonstrated good positioning of graft and implants (Fig. 4). A follow-up computed tomography scan was done that demonstrated a healing fracture and graft incorporation. This type of fracture of the base of the acromion is very rare. The literature shows only case reports, and no formal guidelines exist to fix it, let alone in an OI patient. Case reports of these fractures have been described following reverse total shoulder arthroplasty,9Wahlquist T.C. Hunt A.F. Braman J.P. Acromial base fractures after reverse total shoulder arthroplasty: report of five cases.J Shoulder Elbow Surg. 2011; 20: 1178-1183https://doi.org/10.1016/j.jse.2011.01.029Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar manual lifting,7Rask M.R. Steinberg L.H. Fracture of the acromion caused by muscle forces. A case report.J Bone Joint Surg Am. 1978; 60: 1146-1147Crossref PubMed Scopus (29) Google Scholar carrying weight on shoulder,4Malavolta E.A. Assunção J.H. Sunada E.E. Gracitelli M.E. Neto A.A. A stress fracture of the base of the acromion: a case report.BMC Musculoskelet Disord. 2014; 15: 302https://doi.org/10.1186/1471-2474-15-302Crossref PubMed Scopus (9) Google Scholar and sports such as golfing,8Taneja A.K. Negromonte F.P. Skaf A. Stress injury of the acromion: case report and literature review.Eur J Orthop Surg Traumatol. 2013; 23: 189-192https://doi.org/10.1007/s00590-013-1181-6Crossref Scopus (7) Google Scholar gymnastics,11Warner J.J. Port J. Stress fracture of the acromion.J Shoulder Elbow Surg. 1994; 3: 262-265Abstract Full Text PDF PubMed Scopus (16) Google Scholar and football.10Ward W.G. Bergfeld J.A. Carson Jr., W.G. Stress fracture of the base of the acromial process.Am J Sports Med. 1994; 22: 146-147Crossref PubMed Scopus (37) Google Scholar To our knowledge there has been no report of this rare injury in an OI patient. In most cases, conservative treatment is considered as a first line option.9Wahlquist T.C. Hunt A.F. Braman J.P. Acromial base fractures after reverse total shoulder arthroplasty: report of five cases.J Shoulder Elbow Surg. 2011; 20: 1178-1183https://doi.org/10.1016/j.jse.2011.01.029Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar However, as with any fractures that are treated conservatively, indications for surgery are persistence of symptoms and failure of consolidation of the fracture. When conservative treatment has failed, as it had in our patient, surgical fixation would be the next best option. Choosing a plate for our patient was quite challenging due to a few technical and anatomical points. There was a risk that this bone could provide poor fixation due to the OI; therefore, a locking plate option was essential. Furthermore, a greater number of distal screw fixations was necessary to increase the pull-out strength of our plate construct. In addition, the current readily available standard plates and the traditional LCP plate would not work adequately to provide the crucial stability for bone healing to occur due to the fracture location. We also had limited bone stock/bone thickness to work with. Consequently, we chose to use allograft bone to augment our fixation in addition to locking plate and screws. Augmentation with cortical bone allograft was necessary to allow for screw fixation to achieve the minimum thickness of 10 mm, our shortest screws. Fractures and pseudoarthrosis of the base of the acromion in the setting of OI are exceedingly rare. We utilized a distal tibia anterolateral locking LCP plate with proximal humerus allograft augmentation to provide enough fracture stability for this particular patient. In addition, autograft was used to enhance the capacity of this bone to heal. The innovative use of this tibial locking plate with allograft and autograft allowed bony healing and return to excellent function.

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