Humerus lengthening at a glance
| Question | What the studies report |
|---|---|
| What is lengthened | The humerus, the upper arm bone between shoulder and elbow |
| How | The bone is cut (osteotomy) and then slowly pulled apart (distraction) by an external frame or an internal motorized nail |
| Speed | About 0.6–1 mm a day; the nail review averaged 0.82 mm a day (review), frames typically use 1 mm (Hosny) |
| Typical gain | About 5–9 cm on average, in people whose arms were short |
| Bone healing | Roughly a month per centimetre gained (27–34 days per cm across three series) |
| Main risks | Radial nerve palsy (usually temporary), fracture of the new bone, pin-site infection with frames, stiffness, implant problems |
This page summarises published research. It does not recommend surgery, and it is not medical advice.
Who has humerus lengthening
The studies describe people whose upper arms are short enough to cause problems, or to look clearly out of proportion:
- Achondroplasia and other short-stature conditions. Short arms limit reach and self-care. Lee and colleagues reported better performance in daily activities and sport and a better self-image after lengthening.
- Injury or infection. Damage to the growth plate can leave an arm short (Hosny).
- Bone cysts, complex fractures and brachial plexus (nerve) palsy, the indications in the nail review.
Purely cosmetic lengthening of typical arms is not what these papers study. Even a paper titled cosmetic arm lengthening describes one patient with a shortened humerus, lengthened by 9 cm, and calls it a functional need as well as a cosmetic one.
How the surgery works
- The surgeon cuts the humerus, usually in the middle third of the shaft, and fits a lengthening device.
- After a short pause the device lengthens the bone by roughly a millimetre a day. Nerves, muscles and skin have to stretch with it.
- Once the planned length is reached, new bone (the regenerate) fills the gap and slowly hardens.
- The device comes out when the bone is strong enough, and physiotherapy restores movement.
External frame or internal nail
An external fixator holds the bone with pins that pass through the skin to a frame outside the arm. Pin-track infection was very common in one series of 56 humeri: 46 segments (Hosny). An internal motorized nail, such as PRECICE or FITBONE, lengthens the bone from inside. In a review of 22 nail lengthenings (20 PRECICE, 2 FITBONE) no infections were reported, but 6 of 22 (27%) had other complications such as hardware failure or elbow stiffness. After finding frequent complications with frames, Laufer and colleagues suggest internal devices may be preferable.
How much can the humerus be lengthened?
| Study | Who and how | Average gain |
|---|---|---|
| Lee 2005 | 16 patients, 19 procedures, mean age 11.5 | 5 cm |
| Nail review 2022 | 20 patients, 22 motorized-nail lengthenings | 5.7 cm (range 5–7.5) |
| Ko 2019 | 14 patients with achondroplasia | 7.4 cm |
| Meta-analysis | 14 achondroplasia studies, 1,149 patients (all limbs) | 8.38 cm (95% CI 7.01–9.74) |
| Hosny 2016 | 46 patients, 56 humeri, Ilizarov frame | 9 cm (range 5–15.5), 55% of original length on average |
Every one of these groups began with short arms. A gain that is safe for a short arm says little about an arm of typical length, which no study we found has lengthened. The simulator's slider stops at +8 cm only as a visual range, not as advice.
Recovery and risks
Recovery is long. Bone needs roughly a month per centimetre to heal, and the nail review measured a mean of about 192 days to consolidation. Right after a frame came off, shoulder and elbow movement was temporarily reduced, by 10–35% of the pre-surgery range in Hosny's series, and returned over one to six months (Hosny). In that series everyone returned to their previous work and activities, sport included.
- Radial nerve palsy (wrist and finger weakness): 2 patients in Hosny's series of 46; 39% in a group of 28 children lengthened on both sides. All recovered, within a median of 3 months in the larger group (Laufer 2022).
- Fracture of the new bone: 7 cases among Hosny's 56 humeri (Hosny); refracture in 18% of the bilateral group.
- Pin-site infection with external frames, commonly treated with antibiotics.
- Stiffness, elbow contracture or shoulder problems during lengthening.
- Implant problems with nails, such as hardware failure.
- Unplanned further surgery: 39% in the bilateral group, where half of the children had a major complication. The authors advise limiting the procedure to patients with severe functional impairment.
A pooled analysis of achondroplasia studies found an overall complication rate of 56% across all limbs, with wide uncertainty (meta-analysis). Rates depend on age, method and team, so a surgeon who examines you is the only source for your own numbers.
What longer upper arms do to your proportions
Lengthening the humerus adds nothing to standing height. It changes how long your arms are compared with your height and legs. Arm span is about two arm lengths plus shoulder width, so every centimetre added to both humeri adds 2 cm to arm span.
That matters for proportions. Leg lengthening adds height but not arm span, so it lowers the ape index (arm span minus height). Lengthening the humerus raises it again. Here is the arithmetic for someone 175 cm tall with a 175 cm arm span:
| Scenario | Height | Arm span | Arm span − height | Arm span / height |
|---|---|---|---|---|
| Today | 175 cm | 175 cm | 0 cm | 1.000 |
| Legs +8 cm | 183 cm | 175 cm | −8 cm | 0.956 |
| Legs +8 cm, each humerus +4 cm | 183 cm | 183 cm | 0 cm | 1.000 |
| Each humerus +5 cm only | 175 cm | 185 cm | +10 cm | 1.057 |
The same effect shows in the leg proportions and in arm length as a share of height, which the simulator reports next to your leg ratios.
Preview it on your own photo
Try the Upper arm · humerus slider. Upload a full-body photo and your height, then lengthen or shorten the upper arm and watch the forearm and hand move down your photo or in 3D, next to the leg sliders.
Photos work best with arms hanging slightly away from the body, because the preview moves the forearm and hand as one piece and cannot separate an arm pressed against the torso. Your photo is processed on your device and is never uploaded. The same limb lengthening simulator also previews thigh and shin changes, so you can see arms and legs together. Wondering about a non-surgical option first? Read shoe lifts vs limb lengthening. Looking at the opposite change? See leg shortening surgery.
Sources
- Humerus lengthening with a motorized intramedullary nail: a systematic review of outcomes and complications. Strategies in Trauma and Limb Reconstruction, 2022.
- Hosny GA. Humeral lengthening and deformity correction. Journal of Children's Orthopaedics, 2016.
- Laufer A et al. Risks and functional outcomes associated with bilateral humeral lengthening using a monolateral external fixator in patients with achondroplasia. Clinical Orthopaedics and Related Research, 2022.
- Ko KR et al. Surgical results of limb lengthening at the femur, tibia, and humerus in patients with achondroplasia. Clinics in Orthopedic Surgery, 2019.
- Lee FY et al. Operative lengthening of the humerus: indications, benefits, and complications. Journal of Pediatric Orthopedics, 2005.
- Hosny G et al. Efficacy and safety of limb lengthening in achondroplasia: a systematic review and meta-analysis. International Orthopaedics.
- Agrawal HK et al. Cosmetic arm lengthening with monorail fixator. Chinese Journal of Traumatology, 2015.
Compiled from the papers above and last checked on 29 September 2026; figures are as those papers report them. Talk to a qualified orthopaedic surgeon before deciding anything.