Summary The Proximal Humerus Fixation System (PHFS) from Skeletal Dynamics is a plate-and-peg/screw construct designed around proximal humeral anatomy for fixation of fractures, fracture-dislocations, osteotomies, and non-unions of the proximal humerus. The system centers on a proximal humerus plate with smooth locking pegs, locking/compression screws, and a central fixed-angle peg, with both straight and curved plate options. The PHFS is part of a modular proximal humerus plating platform with multiple plate geometries, accessory plates, and shared screw families Related Implants Plates included in proximal Humerus Fixation System (PHFS) include straight locking plates available with 1, 2, 6, 7, 8, 9, 10 11 shaft slots (75mm - 259mm lengths) curved locking plates available with 5–9 shaft slots (158mm - 254mm lengths) including a “6-slot plus” configuration Indications Indications fractures of the proximal humerus fracture-dislocations of the proximal humerus non-unions of the proximal humerus osteotomies of the proximal humerus Contraindications diaphyseal fractures oediatric fractures tumor reconstruction Relevant Anatomy Osteology the proximal humerus consists of the humeral head, greater and lesser tuberosities, bicipital groove, and metaphyseal/surgical neck. the humeral head has a typical neck–shaft angle of about 135 degrees, which the PHFS reproduces in its fixed-angle peg trajectories. metaphyseal bone quality is often compromised, particularly in elderly osteoporotic patients, emphasizing the importance of secure subchondral fixation . the PHFS has multiple, divergent, fixed-angle pegs oriented toward the humeral head dome to achieve broad subchondral spread and support the articular surface, with the goal of resisting varus collapse. the bicipital groove is an important anterior landmark the plate is positioned just lateral to this groove to align peg trajectories and maintain a safe corridor for the biceps tendon. Muscles rotator cuff muscles influence on fracture patterns and reduction supraspinatus inserts on the superior facet of the greater tuberosity and tends to displace greater tuberosity fragments superiorly. infraspinatus and teres minor insert on the posterior facets of the greater tuberosity, often pulling fragments posteriorly. subscapularis inserts on the lesser tuberosity and can medially displace this fragment. these forces guide fragment-specific reduction strategies and suture placement when using the plate’s suture holes or accessory suture plate. deltoid originates from the lateral clavicle, acromion, and scapular spine and inserts on the deltoid tuberosity. deltoid pull can exacerbate varus and shortening if the shaft is inadequately controlled. during exposure, the anterior deltoid is mobilized proximally in constructs using longer straight plates, partial or total release of the deltoid insertion may be considered for access, followed by repair as appropriate. pectoralis major inserts along the lateral lip of the bicipital groove. release of the proximal third of the tendon can improve exposure of the bicipital groove and proximal humeral shaft, as described in the technique guide. Ligaments the stability of the shoulder is provided by the coracohumeral ligaments glenohumeral ligaments shoulder capsule these ligament structures can be injured in fracture-dislocations the implant does not directly address ligament reconstruction, but reduction and fixation must respect remaining capsuloligamentous attachments. capsular handling should preserve as much viable tissue as possible when head-preserving fixation is planned. Nerves axillary nerve courses around the surgical neck, typically about 5 cm distal to the acromion. at risk during deep dissection and plate application, particularly with long plates. recommended plate positioning 2.5–3.0 cm below the greater tuberosity helps maintain a margin between the distal plate and the usual course of the nerve. musculocutaneous nerve originates from the lateral cord and enters the coracobrachialis on the medial side of the arm. during the deltopectoral approach, the coracobrachialis and biceps are retracted medially with care to avoid tension or compression on the nerve. More distal nerves Radial and ulnar nerves are typically distal to the usual working zone for proximal humerus plating but should be considered when dissection extends far down the shaft. Blood supply The humeral head is perfused by branches of the anterior and posterior humeral circumflex arteries and metaphyseal vessels forming the arcuate artery system. Varus malreduction, excessive head impaction, and circumferential periosteal stripping can jeopardize blood supply and increase the risk of osteonecrosis. The technique emphasizes gentle fragment mobilization, anatomic reduction, and limited stripping where possible to preserve perfusion while obtaining stable fixation. Approach Patient positioning Beach-chair positioning is commonly used, facilitating shoulder manipulation and anatomic orientation for reduction and fluoroscopy. Supine positioning is an alternative when anesthetic or spine considerations favor a flat position and may also facilitate fluoroscopy, depending on setup. The arm is draped free, often on a radiolucent table or shoulder table, with an assistant or mechanical arm holder to provide traction, rotation, and positioning. Skin incision and deltopectoral interval A 12–14 cm oblique incision is made beginning over the coracoid and extending distally toward the deltoid insertion. The cephalic vein is identified and preserved, usually retracted laterally with the deltoid to open the deltopectoral interval. Coracobrachialis and the short head of the biceps are retracted medially to expose the underlying humerus. The pectoralis major tendon insertion is identified; release of the proximal third of this tendon can improve exposure of the bicipital groove and proximal humeral shaft, as suggested in the technique guide. Proximal exposure Subacromial space is developed with careful release of adhesions and bursal tissue to visualize the humeral head and rotator cuff. The proximal deltoid is mobilized as needed, using blunt retractors to avoid muscle and axillary nerve injury. A large humeral head depressor can be placed to improve visualization while protecting the articular surface. Biceps tendon management The long head of the biceps tendon is identified in the bicipital groove. Surgeons may choose tenodesis, tenotomy, or preservation based on patient age, demands, and fracture pattern; this is not dictated by the implant but must be planned around plate position. Fracture debridement and reduction Hematoma, clot, and interposed soft tissue are removed from the fracture site. Fragments are mobilized to allow controlled reduction of the humeral head to the shaft and reapproximation of the tuberosities. Reduction is achieved using traction, manipulation, elevators, joystick techniques, and provisional K-wire or clamp fixation as needed. In comminuted or osteoporotic patterns, heavy nonabsorbable sutures are passed through the rotator cuff tendons and tuberosities early to facilitate reduction and later fixation to the plate or accessory suture plate. Metaphyseal bone grafting may be considered in defects or significant medial comminution. Plating Technique Plate selection and positioning A side-specific plate (left or right) is selected, choosing straight or curved geometry and appropriate length based on the fracture pattern and need for distal fixation. The proximal plate is positioned 2.5–3.0 cm distal to the tip of the greater tuberosity. The anterior straight border of the plate is aligned just lateral to the bicipital groove, aligning the metaphyseal peg trajectories through the humeral head and maintaining space for the biceps tendon. If tuberosity support or anterior buttress is needed, a suture plate or buttress plate is attached to the underside of the proximal plate by engaging the V-channel and securing with a dedicated screw. Provisional plate fixation and central K-wire A 3.2 or 3.5 mm drill is used through the proximal shaft slot to prepare for a 4.5 mm FreeFix compression screw. The compression screw is inserted and fully tightened, providing initial plate-to-shaft fixation while still allowing some translation along the oblong slot for fine adjustment. A threaded K-wire guide is placed into the central post of the plate, and a 2.4 mm K-wire is drilled toward the center of the humeral head. Fluoroscopy in AP and lateral views is used to verify that the wire is center–center and follows the desired 135 degree trajectory. If the K-wire is off-center, it is removed, plate position is adjusted, and the wire is re-drilled until the central position is satisfactory. Metaphyseal peg and screw preparation Polyaxial drill guides (PDGs) are inserted into the metaphyseal holes to direct drilling. For 3.5 mm smooth locking pegs, a 3.5 mm drill is used to perforate the near cortex. For 3.7 mm metaphyseal screws or 3.5 mm variable-angle screws, a 3.0 mm drill is used. The technique guide cautions against advancing drills beyond the cutting flutes to avoid articular penetration. The central K-wire can be bent if necessary to avoid interference with drilling in other holes. Manual safe-tip drilling and subchondral preparation After near-cortex drilling, subchondral preparation is performed with blunt safe-tip drills advanced manually through the PDGs. For pegs, a 3.5 mm blunt-tip drill is used; for screws, a 3.0 mm blunt-tip drill is used. These drills are advanced under fluoroscopic control to just shy of the subchondral bone, with the design intent that the implant tips rest several millimeters below the joint surface. Multiple manual passes can be used to clear bone debris and fine-tune depth. Peg or screw length is determined from the drill scale or with an AIMing guide or depth gauge, depending on surgeon preference and instrumentation. Peg and screw insertion After drilling and measurement, PDGs are removed and the chosen 3.5 mm pegs or 3.7 mm screws are inserted. A T-10 driver is used to seat and lock pegs into the plate. A dedicated peg removal tool can be threaded into the peg after it is loosened with the T-10 driver, allowing controlled extraction without deforming the implant. Central peg preparation and insertion The central K-wire and its guide are removed. A 6.0 mm drill is used under power to perforate the near cortex through a central PDG. A 6.0 mm blunt safe-tip drill attached to a handle is then advanced manually to the subchondral region, again stopping short of the joint surface under fluoroscopic control. Length is measured from the drill scale, and the PDG is removed using the central peg driver. An appropriately sized 6.0 mm smooth locking central peg is inserted and locked into the plate with the T-10 driver to provide a strong central column. Distal shaft fixation Threaded 4.5 mm drill guides or soft-tissue protectors are placed into shaft slots or round holes. A 3.2 or 3.5 mm drill is advanced to the far cortex, and depth is measured with a gauge. FreeFix 4.5 mm compression screws are typically used in oblong slots to compress the plate to the bone and allow small translational adjustments. Once plate position is finalized, 4.5 mm FreeFix locking screws are inserted into round holes to provide fixed-angle diaphyseal support. Tuberosity fixation and closure Heavy nonabsorbable sutures are passed close to the rotator cuff tendon insertions on the tuberosities. These sutures are tied to side, front, or top-loading suture holes in the proximal plate or accessory suture plate to secure the tuberosities to the plate and reestablish the cuff footprint. Final fluoroscopy confirms reduction, peg and screw lengths, plate height relative to the greater tuberosity, and absence of joint penetration or subacromial impingement risk. The wound is closed in layers, with standard soft-tissue and skin closure and postoperative immobilization per surgeon preference. Screws Fixation Strategy Head fixation 3.5 mm variable-angle locking screws Length range approximately 20–70 mm, made of CoCr. Allow controlled deviation from fixed trajectories to target specific bone islands, avoid previous hardware, or accommodate irregular head shape or bone voids. Particularly useful in revision, non-union, or complex fracture patterns. 3.7 mm metaphyseal locking screws Length range approximately 20–70 mm. Alternative to smooth pegs when threaded purchase is desired, such as in sclerotic bone or when re-using drilled holes. Lock into the plate for fixed-angle support similar to pegs. 3.7 mm metaphyseal compression screws Useful when localized compression across a fragment is desired. Can be used to fill remaining metaphyseal holes strategically. 3.5 mm smooth locking pegs Length range approximately 20–70 mm. Main workhorse for humeral head fixation via metaphyseal holes. Used after subchondral preparation with 3.5 mm safe-tip drills to stop short of the joint surface. 6.0 mm smooth locking central peg Length range approximately 30–70 mm. Occupies the central post and provides a strong central column of support. Prepared with 6.0 mm power drilling to the near cortex followed by hand-driven safe-tip drilling to the subchondral region. Shaft fixation 4.5 mm FreeFix compression screws Typical length range 14–40 mm. Used in oblong shaft slots to compress the plate to bone and permit fine translational adjustments before finalizing position. May also be used in round holes when compression is desired along a specific segment. 4.5 mm FreeFix locking screws Typical length range 14–34 mm. Provide fixed-angle diaphyseal support after plate position is finalized. Commonly used in round shaft holes following initial compression. Typical sequencing Initial compression screw in a proximal shaft slot for provisional fixation and plate adjustment. Additional compression or locking screws added distally to complete the construct. Drilling and depth measurement principles Head pegs and screws Initial drilling through PDGs with power drills (3.0 or 3.5 mm) for cortical penetration. Subchondral preparation with blunt safe-tip drills advanced manually to reduce penetration risk. Length determination via drill scale or depth gauges, followed by peg/screw insertion and fluoroscopic confirmation. Central peg 6.0 mm power drilling to the near cortex. 6.0 mm blunt safe-tip drilling by hand toward the subchondral bone. Length measurement and insertion of a central peg sized to rest below the joint surface. Shaft screws 3.2 or 3.5 mm drilling through threaded guides or soft-tissue protectors. Depth gauging and selection of appropriate 4.5 mm screw length. Plate Specifications The PHFS is part of a modular proximal humerus plating platform with multiple plate geometries, accessory plates, and shared screw families. Straight plates Available with 1, 2, and 6–11 shaft slots. Short plates are suited to metaphyseal-focused constructs; longer plates can extend distally for shaft involvement or additional fixation. Straight Plate Dimensions (mm) Plate Length Head Width Head Thickness Shaft Width Shaft Thickness Proximal Humerus Plate, 1 Slot 75 17.4 4.4 14 3.7 Proximal Humerus Plate, 2 Slot 84 17.4 4.4 14 3.7 Proximal Humerus Plate, 6 Slot 163 17.4 4.4 14 4.1 Proximal Humerus Plate, 7 Slot 182 17.4 4.4 14 4.1 Proximal Humerus Plate, 8 Slot 202 17.4 4.4 14 4.1 Proximal Humerus Plate, 9 Slot 221 17.4 4.4 14 4.1 Proximal Humerus Plate, 10 Slot 240 17.4 4.4 14 4.1 Proximal Humerus Plate, 11 Slot 259 17.4 4.4 14 4.1 Curved plates Available with 5–9 shaft slots, including a “6-slot plus” configuration. Curvature is intended to follow the contour of the proximal humeral shaft and match certain patient anatomies or fracture patterns. Curved Plate Dimensions (mm) Plate Length Head Width Head Thickness Shaft Width Shaft Thickness Proximal Humerus Plate, Curved, 5 Slot 158 17.4 4.4 14 4.1 Proximal Humerus Plate, Curved, 6 Slot 177 17.4 4.4 14 4.1 Proximal Humerus Plate, Curved, 6 Slot Plus 196 17.4 4.4 14 4.1 Proximal Humerus Plate, Curved, 7 Slot 215 17.4 4.4 14 4.1 Proximal Humerus Plate, Curved, 8 Slot 235 17.4 4.4 14 4.1 Proximal Humerus Plate, Curved, 9 Slot 254 17.4 4.4 v 4.1 All plates Side-specific (left/right). Standardized proximal head segment with a consistent head width and thickness. Shaft width approximately 14 mm, with thickness varying slightly by plate length. Accessory plates Proximal humerus suture plate Used primarily for tuberosity capture and suture management. Provides dedicated suture holes that interface with the proximal plate. Buttress plate Attaches via a dedicated buttress screw into a “V” channel under the proximal plate. Can provide additional anterior or tuberosity support in comminuted patterns. Shared screw and peg families 3.5 mm smooth locking pegs and a 6.0 mm smooth locking central peg. 3.7 mm metaphyseal locking and compression screws. 3.5 mm variable-angle locking screws as an option when trajectory adjustment is needed. 4.5 mm FreeFix locking and compression shaft screws, shared across the platform. Additional Specifications Materials Plates and standard screws/pegs are titanium alloy. Variable-angle locking screws are cobalt-chromium to provide a strong interface with the VA bushings. Instrumentation highlights Ratcheting and fixed universal quick-connect handles. 2.4 mm Steinmann pins and K-wires with stops for provisional fixation. Polyaxial drill guides for metaphyseal and central post holes. AIMing guides and depth gauges for 2.4 and 3.0 mm drills. Thread-in FreeFix drill guides and pin guides for shaft fixation. 3.0 and 3.5 mm stop drills and corresponding blunt safe-tip drills. 6.0 mm drill and 6.0 mm blunt safe-tip drill for central peg preparation. T-10 and T-15 drivers, peg removal tool, bone holding clamps, and standard retractors. Overall tray organization The dedicated tray is designed to include all tools required for exposure adjuncts, reduction, drilling, peg/screw insertion, and construct adjustment using the PHFS. Pearls & Pitfalls Pearls Use the central K-wire early as a guide for both reduction and plate alignment; adjust plate height and rotation until the wire is truly central before placing additional pegs. Maintain plate position 2.5–3.0 cm below the greater tuberosity to reduce the risk of subacromial impingement and protect the axillary nerve corridor. In osteoporotic or comminuted fractures, combine multiple subchondral pegs with bone grafting in metaphyseal defects to enhance support. Pitfalls High plate positioning can cause impingement and still leave inadequate room for subchondral support. Driving power drills past their flutes risks articular penetration; rely on hand-driven safe-tip drills for final subchondral preparation. Accepting varus malreduction compromises mechanics and fixation; correct varus alignment before locking in the construct.