The versatility of the proximal humeral internal locking system plate in orthopedic surgery: A comprehensive review of its off-label applications

Periprosthetic humerus fractures

The rising incidence of shoulder arthroplasty has led to an increase in periprosthetic humerus fractures.^[12,13] The PHILOS plate has been applied in some specific cases where open reduction and internal fixation (ORIF) is indicated [Table 1 and Figure 1a]. A study reported preoperative and post-operative results in three patients who underwent ORIF for a periprosthetic humeral fracture around a well-fixed short-stem anatomic total shoulder arthroplasty using the PHILOS plate.^[13] All three patients received the treatment with a proximal humeral locking plate, achieved fracture union, and had radiographic healing confirmed within 3–12 months. Postoperatively, they demonstrated significant pain relief and improved range of motion (ROM). The authors concluded that the PHILOS plate enables both unicortical and bicortical screw fixation around the humeral implant, enhancing stability compared to conventional locking compression plate (LCP) designs. Another case involving a 78-year-old woman who presented with a periprosthetic humeral fracture and had a history of onlay-type reverse shoulder arthroplasty was treated with ORIF by using a 9-hole long PHILOS plate. Fracture union was observed at 5 months post-fixation, with complete recovery. The authors concluded that the PHILOS plate allows for the placement of locking screws into the remaining greater tuberosity, which can be challenging with larger locking plates. Furthermore, it enables fracture site compression through a dynamic compression screw after securing the proximal fragment to the plate.^[12]

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Figure 1:

Application of a proximal humeral internal locking system (PHILOS) plate in the humerus. (a) Radiographic image demonstrating periprosthetic fracture fixation in the proximal humerus around a Bilboquet implant. (b and c) Anterior application of a PHILOS plate on the distal humerus, shown on a Sawbone model.

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Application of the PHILOS plate in managing the distal humerus

PHILOS plate could successfully treat distal humerus fractures [Table 1], including extra-articular distal-third diaphyseal humeral fractures, by application of the plate at the anterior cortex of the humerus [Figure 1b and c]. Sohn and Shin^[14] evaluated the modified use of the PHILOS plate in extra-articular distal-third diaphyseal humeral fractures, utilizing an inverted application in the anterior cortex with open plating or anterior minimally invasive plating osteosynthesis (MIPO) techniques. All 23 patients achieved fracture union at a mean of 20.8 weeks, with an average Mayo Elbow Performance score of 97.6. The study highlighted the plate’s effectiveness in increasing plate-screw density and achieving stable fixation in distal humeral fragments with no complications requiring reoperation.

Another study investigated the anterior MIPO technique using a reversed PHILOS plate in twelve patients with multifragmentary distal humeral shaft fractures. All patients achieved fracture union within an average of 14.8 weeks, with no perioperative complications. The study reported excellent functional outcomes. The authors concluded that this technique is a safe and effective option, even in cases with as little as 2 cm of intact bone proximal to the coronoid fossa.^[15]

PHILOS plate application in the proximal femur in children

The pre-contoured design of the PHILOS plate conforms to the anatomy of the proximal femur in the pediatric population. The PHILOS plate offers several advantages, including a broad proximal end that enhances fixation strength in the proximal femur. In addition, its proximal holes accommodate screws at a 130-degree angle, aligning with the femoral neck-shaft angle. Moreover, multiple screw holes allow for secure fixation toward the femoral head, providing stability without requiring transphyseal fixation. Furthermore, the PHILOS plate can be applied using the MIPO technique, which preserves soft-tissue integrity, minimizes periosteal stripping, and reduces vascular damage and post-operative scarring.^[16]

Gogna et al. evaluated the use of long PHILOS plates for fixation of pediatric subtrochanteric femoral fractures in 8 patients aged 10–16 years with a mean follow-up of 32 months.^[16] All fractures achieved union at an average of 8.75 weeks. The main complication was prominent hardware, with one requiring implant removal.^[16] Suresh et al. successfully treated a pediatric comminuted subtrochanteric femur fracture using a PHILOS plate with the MIPO technique, achieving uneventful healing.^[17] Danişman et al. evaluated the use of the PHILOS plate for subtrochanteric femur fractures in nine pediatric patients, reporting a mean union time of 8.2 weeks with no complications and satisfactory outcomes.^[18] Newbury et al. successfully treated a pathological subtrochanteric femur fracture caused by an aneurysmal bone cyst in a 14-year-old using a PHILOS plate and bone grafting, achieving complete healing without complications at a 2-year follow-up.^[19] Cortes et al. reported the successful treatment of a pediatric subtrochanteric femur nonunion in an 11-year-old boy using a PHILOS plate.^[20] The plate provided adequate proximal fixation and bridged previous distal screw holes. Bone union was achieved without complications. Taşatan and Tekin retrospectively assessed the use of PHILOS plates in 24 patients aged 11–15 years with intertrochanteric femoral fractures.^[21] All fractures achieved union within a mean of 12.8 weeks, with no complications except for two cases of superficial wound infections that resolved within 10 days. Clinical and functional outcomes were favorable. Shaw et al. reported the successful use of a PHILOS plate for the fixation of a pediatric periprosthetic femoral fracture adjacent to a previously implanted blade plate in an 18-year-old patient with cerebral palsy.^[22] The patient was treated with ORIF using a 10-hole PHILOS plate. Radiographic union was achieved at 11 months, with no post-operative complications.

Based on the available evidence from multiple studies, the authors concluded that the PHILOS plate is a versatile and effective option for managing pediatric proximal femoral fractures, including complex, subtrochanteric, intertrochanteric, and revision cases. Its anatomical design, stable fixation, and compatibility with MIPO techniques support high union rates, early mobilization, and minimal complications.

PHILOS Plate application in the proximal femur in the adult population

The PHILOS plate has demonstrated efficacy in managing proximal femur cases, including periprosthetic fractures, subtrochanteric osteotomies, and post-polio fractures [Figures 2a and b]. Yun et al. investigated the biomechanical efficacy of PHILOS plates in Vancouver B1 periprosthetic femoral fractures compared to cable greater trochanteric reattachment (GTR) plates through clinical evaluation, finite element analysis, and mechanical testing using Synbone femoral models.^[23] The study included 18 patients, all of whom achieved fracture healing. Biomechanical testing demonstrated that PHILOS plates provided superior stability, particularly under high-load conditions. The study supports PHILOS as a reliable, cost-effective alternative for managing Vancouver B1 fractures.

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Figure 2:

Application of a proximal humeral internal locking system (PHILOS) plate in the femur. (a) PHILOS plate applied to the proximal femur. (b) Radiographic image demonstrating periprosthetic fracture fixation in the proximal femur. (c) PHILOS plate applied to the medial condyle of the distal femur. (d) PHILOS plate applied to the lateral condyle of the distal femur.

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Çağlar et al.^[10] retrospectively evaluated the use of PHILOS plates for the fixation of subtrochanteric femoral shortening osteotomy (SFSO) during total hip arthroplasty in 30 female patients with Crowe type IV developmental dysplasia of the hip.^[24] The mean union time was 106 days, with one nonunion successfully revised using a longer PHILOS plate and autograft. No implant failures or irritation were reported. The authors found outcomes comparable to standard methods, concluding that the PHILOS plate is a viable option for stable SFSO fixation and effective rotational control.

Reports have indicated that post-polio femoral fractures could be fixed with the use of PHILOS plates to a great extent.^[8] Patients with post-polio syndrome (PPS) are particularly characterized by severe osteopenia, decreased vascularity, muscle atrophy, and a small, deformed distal femur.^[8,25,26] Consequently, conventional lateral plates may be too large, risking instability and hardware irritation. Pires et al.^[8] successfully used a PHILOS plate to treat a subtrochanteric fracture in a 37-year-old PPS patient. Given the severe osteopenia and thin femoral structure characteristic of PPS, conventional lateral locking plates were deemed unsuitable. Bone union was achieved within 5 months without complications.^[8] The study highlights the PHILOS plate as a viable alternative for managing proximal femoral fractures in patients with PPS.

Application of the PHILOS plate on the medial femoral side

The PHILOS plate has been explored as an alternative fixation method for distal femur fractures, particularly in complex cases. It conforms to the medial femoral condyle and allows for the placement of multiple locking screws, providing stable fixation for medial femoral condyle fractures. A biomechanical study compared the PHILOS plate with other LCP tibial plates for medial femoral condyle fractures [Figure 2c]. The PHILOS plate allowed for the maximal number of screw insertions, while the force required for 2 mm displacement showed no significant difference between plates.^[27] However, its use as the sole fixation method in bicondylar fractures with meta-diaphyseal extension is not recommended due to its insufficient mechanical strength.^[8]

According to reported studies, using a PHILOS plate in conjunction with a lateral distal locking plate has been suggested for elderly patients with periprosthetic fractures following total knee arthroplasty (TKA).^[8,28] TKA periprosthetic fractures are particularly challenging due to poor bone quality, short metaphyseal fragments, and the constraints imposed by the prosthesis.^[29] When these fractures involve the distal femur, they often present with short lateral meta-epiphyseal fragments and a larger medial fragment. In such cases, combining a PHILOS plate with a long lateral distal locking plate has been recommended to mitigate potential clinical complications in elderly patients.

Pires et al. reported two complex distal femur fracture cases successfully treated with PHILOS plates.^[8] A medial condyle gunshot fracture was fixed with an inverted PHILOS plate, and a Rorabeck type II periprosthetic fracture was stabilized using a medial PHILOS plate with a lateral LCP. Both cases achieved stable fixation and early recovery, highlighting the value of the PHILOS plate in challenging distal femur scenarios. Another study by Park et al. investigated using dual plating with the MIPO technique for TKA periprosthetic fractures.^[30] They treated 18 patients using a lateral LCP and a medial PHILOS plate, reporting an average union time of 18.4 weeks, with no cases of nonunion or implant failure. At the 1-year follow-up, patients demonstrated satisfactory clinical and radiological outcomes, with an average knee ROM of 110.3. The study supports dual plating as a reliable technique for managing these complex fractures, with the PHILOS plate providing additional stabilization in both the coronal and sagittal planes. Poelmann and Kloen evaluated the use of the PHILOS plate as a medial buttress for distal femoral nonunions.^[31] In a cohort of 15 patients, their technique achieved an 80% union rate, with a median healing time of 4.8 months. Three patients required additional bone grafting, and one underwent quadricepsplasty. The study suggests that the PHILOS plate is a safe and effective option for medial support in the treatment of distal femoral nonunions.

Application of the PHILOS plate on the lateral femoral side

The application of the PHILOS plate on the lateral distal femoral surface has been evaluated in two studies [Figure 2d]. Abdelgawad and Kanlic examined its use for distal femoral metaphyseal fractures in two adolescent patients, positioning the plate laterally, proximal to the physis, with no transphyseal screw placement.^[32] Both fractures healed with good alignment and full knee ROM. Another study assessed dome osteotomy with PHILOS plate fixation on the lateral condyle for genu valgum in late adolescents and young adults, involving 27 knees.^[33] The study reported complete union in all cases within 6–8 weeks. Both studies support the PHILOS plate as a stable and effective option for femoral fracture fixation and deformity correction in adolescents and young adults.

Application of the PHILOS plate in distal tibia and fibula fractures

In the ankle region, the primary challenges include deformity, compromised bone quality, and suboptimal soft-tissue conditions, all of which can significantly impact surgical outcomes. This is why several studies [Table 1] have proposed the applicability of PHILOS plates, as they are characterized by a low profile with numerous locking screw options, thereby increasing the stability of the construct and the conditions for healing [Figure 3].^[8,11,34-36]

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Figure 3:

Application of a proximal humeral internal locking system (PHILOS) plate demonstrating different plate positioning on a bone model around the foot and ankle region. (a and b) Medial placement on the distal tibia. (c and d) Posterior placement on the distal tibia. (e and f) Placement on the lateral malleolus. (g) Posterior application for ankle arthrodesis. (h) Radiographic image showing a PHILOS plate used for ankle arthrodesis via a posterior approach for a comminuted pilon fracture. (i and j) Lateral placement on the ankle-hindfoot complex for TTC arthrodesis.

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The PHILOS plate has been used for lateral malleolus fractures with promising results. In a series of 13 patients, Hasan et al.^[34] reported a mean union time of 8.5 weeks, with one case of superficial infection and two cases requiring implant removal due to persistent pain. The authors concluded that while the PHILOS plate is not the only or best fixation method, it provides significant advantages, particularly in osteopenic bone, making it a reasonable option for lateral malleolus fractures.

Regarding using PHILOS plates in tibial fractures, a study has reported three osteosyntheses utilizing a reverse PHILOS plate for ankle fractures and tibial pilon fractures, employing both short and long PHILOS plates.^[35] In this case series, which included three patients, the plate was applied to the medial cortex (in one patient) and the posterior cortex (in two patients) of the distal tibia. The study reported successful primary wound healing and fracture consolidation without complications, suggesting that the PHILOS plate may serve as a viable alternative for distal tibial fixation, particularly in complex fracture patterns. Twaij and Damany reported successfully using a PHILOS humeral plate as an alternative implant for the emergency fixation of a distal tibial fracture.^[36] Due to the unavailability of a standard distal tibial locking plate, the PHILOS plate was adapted intraoperatively, providing stable fixation with locking screws in the medial malleolar fragment. The patient achieved full recovery with satisfactory outcomes at 4 months. The authors suggest that, in cases where standard implants are unavailable, the PHILOS plate may serve as a viable alternative for stabilizing distal tibial fractures. In another study where a locking distal tibial plate was unavailable, a PHILOS plate was utilized as an alternative to treat a medial malleolar fracture.^[36] The PHILOS plate assisted in the stabilization of the distal tibial fracture by facilitating the surgeon to insert locking screws into the medial malleolar fragment. The patient made a complete recovery and demonstrated acceptable improvement at the 4-month follow-up, making the PHILOS plate an effective alternative option in emergency trauma cases. A study conducted explored the application of the PHILOS plate for distal tibial fractures, including isolated malleolar, bimalleolar, and tri-malleolar fractures.^[11] In this study, 20 patients underwent ankle fracture fixation using a PHILOS plate as an alternative due to the unavailability of the standard fixation plate. The findings demonstrated a 100% fracture union rate at the 12-month follow-up, with all patients achieving full ankle ROM by 12 weeks postoperatively and no reported complications.

Ankle arthrodesis and tibiotalocalcaneal (TTC) arthrodesis

TTC arthrodesis is a salvage procedure indicated for severe hindfoot pathology. It aims to restore alignment, alleviate pain, and provide stability in cases where conventional fixation methods are inadequate. The PHILOS plate has been increasingly utilized in TTC arthrodesis due to its biomechanical stability and ability to accommodate multiple locking screws, enhancing fixation in osteoporotic bone. Several studies have explored using the PHILOS plate for TTC arthrodesis via a lateral transfibular approach.^[8,9,37-39] Fan et al. reported a 100% fusion rate in 12 patients undergoing TTC arthrodesis with a reverse PHILOS plate and medial cannulated screws, with a mean of the American Orthopaedic Foot and Ankle Society (AOFAS) score of 77.5.^[37] Similarly, Shearman et al. assessed the technique in 21 patients, achieving an 85.7% fusion rate with a mean union time of 4.8 months, though a 14.3% deep infection rate was noted.^[38] Zhang et al. investigated TTC arthrodesis in 15 patients using an inverted PHILOS plate.^[39] Fusion was achieved in all but one patient, who required secondary bone grafting for delayed union. The average fusion time was 16.8 weeks, resulting in significantly improved AOFAS and Visual Analog Scale. Ahmad et al. evaluated its use in 17 patients, demonstrating a 94.4% fusion rate and significant functional improvements, particularly in osteoporotic bone.^[9] Özer et al. examined PHILOS plate fixation in eight patients with hindfoot arthrosis, reporting an 87.5% fusion rate over a mean follow-up of 32.6 months.^[40] Cabrera Méndez et al. evaluated TTC arthrodesis using a PHILOS plate in 35 patients.^[41] The study reported a mean union time of 4.37 months, with complications including delayed union in three cases and surgical site infection in four. The findings suggest that this technique offers effective fixation with a low complication rate and satisfactory post-operative outcomes.

In addition to TTC arthrodesis, the PHILOS plate has also been utilized for early ankle arthrodesis in cases of severely comminuted tibial pilon fractures, where primary fusion is considered to prevent long-term complications. Samargandi et al. evaluated early ankle arthrodesis using an inverted PHILOS plate through a posterior approach in nine patients with severe comminuted tibial pilon fractures.^[42] The study reported an 89% union rate, no infectious complications, and a mean AOFAS score of 66, suggesting this technique is a reliable alternative for achieving union in complex fractures. Similarly, Pires et al. described a case of primary ankle arthrodesis using a PHILOS plate on the posterior tibial surface, demonstrating successful fusion and highlighting the implant’s adaptability in ankle reconstruction.^[8] Aneja et al. reported a case of tibiotalar fusion in a 70-year-old patient with a severe comminuted pilon fracture, in which a tensioned proximal humerus plate was used due to the inadequacy of standard fusion plates to span the fracture site.^[43] The authors suggest that this technique may be a viable alternative in cases with extensive distal tibial comminution. Collectively, these studies support the PHILOS plate as a viable alternative for both ankle and TTC arthrodesis, providing stable fixation and high fusion rates in complex cases.