Minimally invasive plate osteosynthesis (MIPO) for scapular fractures

Objective Presentation of a minimally invasive surgical approach for the treatment of scapular fractures and the clinical outcome using this technique. Indications Displaced extra-articular fractures of the scapula body and glenoid neck (AO 14B and 14F) and simple intra-articular fractures of the glenoid. Contraindications Complex intra-articular fractures and isolated fractures of the coracoid base. Surgical technique Make a straight or slightly curved incision along the lateral margin of the scapula leaving the deltoid fascia intact. Identify the interval between the teres minor muscle and infraspinatus to visualize the lateral column, whilst retracting the deltoid to visualize the glenoid neck. Reduce and align the fracture using direct and indirect reduction tools. A second window on the medial border of the scapula can be made to aid reduction and/or to augment stability. Small (2.0–2.7 mm) plates in a 90° configuration on the lateral border and, if required, on the medial border are used. Intra-operative imaging confirms adequate reduction and extra-articular screw placement. Postoperative management Direct postoperative free functional nonweight-bearing rehabilitation limited to 90° abduction for the first 6 weeks. Sling for comfort. Free range of motion and permissive weight-bearing after 6 weeks. Results We collected data from 35 patients treated with minimally invasive plate osteosynthesis (MIPO) between 2011 and 2021. Average age was 53 ± 15.1 years (range 21–71 years); 17 had a type B and 18 a type F fracture according the AO classification. All patients suffered concomitant injuries of which thoracic (n = 33) and upper extremity (n = 25) injuries were most common. Double plating of the lateral border (n = 30) was most commonly performed as described in the surgical technique section. One patient underwent an additional osteosynthesis 3 months after initial surgery due to pain and lack of radiological signs of healing of a fracture extension into the spine of the scapula. In the same patient, the plate on the spine of scapula was later removed due to plate irritation. In 2 patients postoperative images showed a screw protruding into the glenohumeral joint requiring revision surgery. After standardisation of intra-operative imaging following these two cases, intra-articular screw placement did not occur anymore. No patient suffered from iatrogenic nerve injury and none developed a wound infection.


Introductory remarks
Scapula fractures typically result from high-energy trauma and are often associated with other thoracic or upper extremity injures.Non-or minimally displaced fractures can be treated conservatively; however, malalignment of the glenoid neck (a sharpened glenopolar angle, GPA) and intra-articular malunion can lead to impingement, rotator cuff dysfunction, osteoarthritis and, consequently, poor functional outcome [1,2,3].The scapula functions as a dynamic stabilizer for the humerus-shoulder complex and therefore malunion induces chronic loss of endurance, strength and muscle reaction capacity Over the last few decades, open reduction and internal fixation according to AO principles is increasingly applied to restore the GPA, articular congruency and alignment.Cole et al. described a well differentiated assessment algorithm to determine when surgery is indicated [1].
The most common approaches for the treatmentof scapulafractures aretheJudet and the modified Judet approach, first described in 1964 [2].The main advantage of the Judet approach is complete exposure of the posterior aspect of the scapula body.However, this requires a large skin incision and extensive muscular disruption by release of the Infraspinatus as well as the deltoid muscle.Furthermore, the large reflected muscle flap of the infraspinatus impedes articular visualisation and can create tension on the suprascapular nerve.The modified Judet approach uses the same incision as its traditional counterpart; however, it uses windows between the infraspinatus and teres minor to approach the fracture (instead of release of the deltoid muscle and infraspinatus).Cole et al. showed that this less invasive approach only reduces the view on the lateral column by 9% [3].Nevertheless, it still requires an extensive cutaneous incision with the inherent risk of complications (e.g.seroma, cutaneous nerve injury, increased risk of superficial infection and aesthetic concerns).
Gauger and Cole described a minimal invasive approach working through soft tissue windows in 2011 [3].Their outcomes were promising and extended the indicationfor surgical managementintheir and our practise.In our institute the technique has been applied for approximately 10 years.
The aim of the current paper is to enhance awareness of this approach and present our clinical experience with this technique.

Surgical principles and objective
The minimally invasive plate osteosynthesis of scapula fractures allows for adequate fracture reduction through soft tissue windows without need to release any muscles including the posterior portion of the deltoid.Different soft tissue windows (over the lateral and medial border, as well as over the spina scapulae) are used to approach the scapula.Appropriate padding of the chest and the uninjured arm is necessary.The affected arm is draped free on a padded arm support or is held by a pneumatic arm holder allowing intraoperative limb positioning to aid reduction and imaging (.Fig. 1).-Fluoroscopy should be positioned perpendicular to the patient and table, entering from the cranial (or alternatively anterior/front) side of the patient.Preoperative trial imaging should be performed to confirm the ability to achieve a proper scapular Y view and an anteroposterior (AP) view of the shoulder (.Fig. 2).Fig. 8 8 a In case of a comminuted lateral border in which rigid fixation is not possible or medial displacement (> 1 cm), an additional incision over the medial margin is performed.The medial incision and precedent reduction of the the margo medialis is made neutralizing the medial-lateral displacement of the scapular body fragment and adding reduction.Addressing the medial side first might also be beneficial in cases of severe comminution of the lateral margin where no good reference for reduction can be obtained.If required, additional windows can be made over the spina scapulae, in case of fractures extending to this part of the scapula.bThe intra-operative images show fracture reduction using four 2.7 mm plates

Postoperative management
Direct postoperative radiographs are recommended to assure an adequately reduced fracture and correct implant position.A sling is provided for comfort, pain control and soft tissue healing.Under supervision of a physiotherapist, assisted thoraco-scapular mobilization and range of motion exercises respecting pain perception are allowed.Resistance training and weight bearing will be allowed after the first outpatient follow-up after 6 weeks.Expected return to work ranges from 2 weeks, in case of desk job, but up to 3 months in case of physically demanding work.

Errors, hazards, complications
-Screw perforation into the glenohumeral joint -Damage to the supraclavicular nerve running through the spinoglenoid notch caused by either traction or a malpositioned Hohmann retractor -Damage to the axillary nerve running through the interval between teres major and minor

Outcome institution and literature
We collected data of 35 patients treated with minimally invasive plate osteosynthesis (MIPO) between 2011 and 2021.The median follow-up was 8 months (range 3-31 months).All patients sustained high energy trauma (injury severity score > 16) and were predominantly male (only 1 female).Average age was 53 ± 15.1 years (range 21-71); 17 had a type B and 18 type F fracture according the AO/OTA classification.All patients suffered concomitant injuries of which thoracic (n = 33) and upper extremity (n = 25) injuries were most common.Average time to surgery was 6 ± 4 days (0-17 days; .Fig. 9).Predominantly double plating (n = 30) was performed using either a 2.0 mm or 2.7 mm plate to maintain reduction and a larger 2.7 mm plate (or 3.5 mm reconstruction plate in the period prior to 2019) for stability.Average time to union was 21.5 ± 8.5 (range 11-36) weeks.One patient underwent an additional osteosynthesis 3 months after initial surgery due to pain and lack of radiological signs of healing of a fracture extension into the spina scapulae.In the same patient the plate on the spina scapula was later removed due to plate irritation.In 2 patients postoperative images showed a screw protruding into the glenohumeral joint requiring revision surgery.After standardisation of intra-operative imaging following these 2 cases, intra-articular screw placement did not occur anymore.No patient developed an infection or sustained iatrogenic nerve injury.
To the best of our knowledge two studies investigated outcomes specifically for minimally invasive plate fixation for scapular fractures [3,4].Gauger et al. published their retrospective case series of 7 male patients with a mean age of 39 years (range 19-75 years) and follow-up of a minimum 12 months and reported comparable re-sults to our study [3].The mean DASH score was 8.1 (range 0-52).Strength and motion returned to equivalency with the uninjured shoulder.The retrospective cohort study of Mannambeth et al. included 11 patients (10 men) with a mean age of 45 years (range 24-67 years) and followup of 16 months (range 12-28 months) [4].They also demonstrated similar outcomes: The mean DASH score was 11.4 (range 0-51).Almost all patients returned to work after an average of 3.3 months (range 2 weeks-8 months).One patient did not because of concomitant brachial plexus injury.All fractures healed in their cohort without infections or nerve injury.

Fig. 1 8
Fig. 1 8 a Positioning of the patient and C-arm.b Patient after draping

Advantages----
Minimal disruption of subcutaneous tissue and posterior scapula musculature -Potentially reduced risk of suprascapular and deltoid nerve injury due to deltoid muscle sparing approach -Improved cosmetic outcomes Disadvantages Limited vision of the surgical field, especially if sufficient muscle relaxation has not been acquired -Technically demanding -Limited control of fracture fragments Indications The treatment decision should be based not only on the fracture pattern but also on the needs of the individual patients.The following indications according to Cole et al. may serve as a guideline for the application [1]: -Glenopolar angle < 22°-> 20 mm medial-lateral displacement (MLD) of the glenohumeral part -Angular deformity > 45°or > 30°in combination with MLD > 15 mm -Intra-articular step-off > 4 mm -> 10 mm MLD in combination with additional disruption of the superior shoulder suspensory complex.Contraindications Complex intra-articular fractures -Fracture of the scapula process (AO 14A) Patient information General surgical risks -Implant-related complications (e.g.loss of reduction, screw perforation) -Injury to the nerves (suprascapular and axillary) -Implant removal Preoperative work-up -Clinical examination especially of motor and sensory function of the brachial plexus (including axillary and suprascapular nerve) -A preoperative computed tomography (CT) scan including three-dimensional (3D) reconstructions is strongly recommended for fracture assessment and adequate planning Operative Orthopädie und Traumatologie 6 • 2023 391 Instruments -Standard surgical instruments for soft tissue procedures and osteosynthesis -Large and small pointed and blunt reduction forceps -2.0, 2.4, 2.7 mm LCP plates and screws, K-wires (1.2 and 1.6 mm) -Push-pull instruments (ball spike, bone hook, Schanz screws) -Minidistractor or minimally invasive (MI) reduction tools Anaesthesia and positioning -General anaesthesia with adequate muscle relaxation is mandatory -Lateral position is preferred to prone.It allows for better control of arm position that can aid reduction and permits using the coracoid for the placement of an additional percutaneous joystick if needed to facilitate reduction in scapular neck fractures.-Place the patient on the cantilevered end of a radiolucent operating table.