One of the most prevalent endocrine conditions is primary hyperparathyroidism. One acute presentation that revolves around hypercalcemic homeostasis is typically used to establish the diagnosis ^[1]. In the past 20 years, indolent forms involving the bones have hardly been seen, and the characteristics that coincide with dystrophies, skeletal dysplasia, and cancers may make diagnosis more difficult ^[2,3]. 2–3% of all neck of femur fractures in people under 50 are femoral neck fractures ^[4]. High-energy trauma accounts for the majority of fractures in this age range ^[4,5]. In young adults, bilateral atraumatic femoral neck fractures occurring simultaneously are regarded as extremely uncommon occurrences. There were not many cases in this age range documented in the literature ^[6,7]. Avascular necrosis and non-union are among the consequences linked to these fractures ^[8,9]. Anatomical reduction, early fixation, and rehabilitation are crucial to avoid such devastating complications. We report this rare case of bilateral neck of femur fracture in a young adult, along with varied manifestations of metabolic bone failure that are pathognomonic of hyperparathyroidism. We also highlight the current evidence-based practices in the management of various bony manifestations.

A 26-year-old male patient came in with a history of bilateral hip pain that had been ongoing for 4.5 years. His medical journey began with a referral from the endocrinology department after the removal of a right inferior parathyroid adenoma (RIPA) 2 years prior. This adenoma was discovered incidentally while evaluating his generalised weakness and persistent bilateral hip pain, which had started 2 years before the surgery. When he presented, he reported that the hip pain had continued for 4.5 years. About 4.5 years ago, he had been asymptomatic until he developed hip pain, which also led to a noticeable change in his gait. Radiographic imaging showed atraumatic fractures in both hips. In addition, the patient has been experiencing intermittent abdominal pain for the past year, described as nausea and vomiting, localised to the flank without any radiation to the back. In the 2 years leading up to his referral, he reported symptoms including anorexia, weight loss, muscle mass loss, and general fatigue. His medical history includes the removal of a benign tumour beneath the left molar tooth, thought to be an epulis, 9 years ago. After the excision of RIPA in 2022, the findings are summarised in Table 1.

Table 1: Serial laboratory investigations before and after parathyroid adenoma excision

The patient was diagnosed with “hungry bone syndrome” and was treated with replacement therapy. His overall condition improved and stabilised with the administration of parenteral calcium gluconate and neutral phosphate. On examination, the patient was found to be conscious, cooperative, and orientated, with a Glasgow Coma Scale of E4V5M6. Systemic examination findings include: Weight: 54 kg, height: 152 cm, body mass index: 19 kg/m,² AS: 160 cm, US: LS 75:88 cm (−0.85), and a scar mark noted. Central nervous system: E4V5M6, motor power assessed at 5/5 in both lower limbs and upper limbs bilaterally, reflexes graded at 2+ for triceps, biceps, knee, and ankle; plantar reflex is flexor. The patient has lost three molar teeth in the left jaw and exhibits lordosis with a bilateral waddling gait, along with a scar mark on the abdomen. An initial physical examination of the hips revealed a negative Patrick test, full range of motion, and mild soreness in the groin area; the Harris Hip Score was 60 in both hips. Generalised muscle atrophy was noticed. The plain radiographs revealed bilateral neck of femur fractures (both of which were graded as Type IV according to Garden’s classification) with multiple small cysts in the femoral head and acetabulum; moderate joint space narrowing features suggesting osteoarthritis (OA) and overriding of the greater trochanter; generalised osteoporosis; and multiple lytic lesions in the tibia and pelvis, along with regional changes like severe anterolateral bowing of the femur (Fig. 1), salt-and-pepper skull, kyphoscoliosis in the spine with cod-fish and rugger jersey appearance (Fig. 2) and acro-osteolysis of the hand (Fig. 3).

Figure 1: Hip joint (bilateral neck of femur fracture and osteoarthritis changes).

Figure 2: Spine (kyphoscoliosis in the spine with cod-fish and rugger jersey appearance).

Figure 3: (Acro-osteolysis of hand).

All these metabolic changes in the skeleton as identified in the imaging studies are summarised in Table 2.

Table 2: Imaging studies

The patient underwent optimisation and was deemed suitable for surgical intervention a few days following admission. A total hip arthroplasty (THA) was indicated due to the presence of established OA changes. Our senior consultant (AA) decided to perform a hybrid THA, utilising an uncemented cup and a cemented stem, in light of the observed cortico-medullary irregularities in the femur (Fig. 4).

Figure 4: Post-operative X-ray.

Postoperatively, the patient remained non-weight-bearing on both legs for 4 days. Subsequently, he began knee-bending exercises, practised side-sitting, and was assisted in walking with a walker under supervision. He was ultimately discharged in an improved condition. Subsequent follow-ups at 1 month, 3 months, 6 months, and 1 year revealed that the patient could walk independently and bear weight fully, exhibiting no limping and a pain-free gait. He was able to walk and run slowly but was unable to squat. Approximately 12 months later, the patient returned for another evaluation. He was able to walk without a limp and reported no further pain. Daily activities were performed within the permissible range of motion associated with total hip replacement. An X-ray indicated a normal right hip with the implant in place after 1 year (Fig. 5). The Harris Hip Score improved to 90 on both sides, and the left hip’s range of motion increased to 120° of flexion. Impingement tests yielded negative results, and flexion, abduction, and external rotation were within normal limits.

Figure 5: One-year follow-up X-ray.

Parathyroid adenomas, especially solitary ones, are the predominant cause of primary hyperparathyroidism, with adenomatous parathyroid tissue often located in ectopic sites ^[10]. Approximately 5% of these adenomas are identified in the mediastinum, with 95% of those situated within the thymus ^[11]. Post-operative hypocalcemia is frequently observed in the early stages following parathyroid surgery. A specific condition known as “hungry bone syndrome” can lead to significant hypocalcemia immediately after surgery, which may prove resistant to treatment. While mild hypocalcemia can often be managed with oral calcium supplements, severe cases necessitate parenteral calcium administration. Skeletal involvement in primary hyperparathyroidism is estimated to occur in about 2% of cases ^[12]. Evidence supporting the notion that reduced bone density due to hyperparathyroidism correlates with a higher fracture rate is limited Wilson et al., ^[13]. Found no significant increase in vertebral fractures among 174 hyperparathyroid patients, whereas Peacock ^[14] reported a higher incidence of both vertebral and cortical fractures in this population. The occurrence of femoral neck fractures resulting from ectopic parathyroid adenomas is exceedingly rare, and prompt surgical intervention is essential to mitigate the risks of non-union and avascular necrosis ^[15].

This case highlights the severe skeletal manifestations that can result from delayed diagnosis of primary hyperparathyroidism, including bilateral femoral neck fractures in a young adult. Despite advancements in diagnostic modalities, indolent presentations involving bone metabolism continue to occur and can lead to significant morbidity if not recognised early. Comprehensive endocrine evaluation in young patients with unexplained musculoskeletal symptoms is essential. Timely surgical and orthopaedic interventions, combined with metabolic correction, can lead to favourable functional outcomes even in advanced cases.

In young patients presenting with unexplained bone pain or fragility fractures, especially in the absence of trauma, clinicians should consider underlying metabolic bone disorders such as primary hyperparathyroidism. Early diagnosis and multidisciplinary management are crucial to prevent severe skeletal complications and optimize patient outcomes.